The 1981 Buick Century rides on GM's A-body platform with a range of powertrains from the reliable 231 V6 to the infamous 350 diesel. Most problems center on the 200-4R/TH200C transmissions, engine mount failures, and catastrophic diesel engine issues.
TH200C/200-4R Transmission Failure
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: Slipping between gears, especially 2nd to 3rd, Delayed engagement when shifting into drive, Whining or grinding noises under acceleration, Transmission fluid dark and burned-smelling
Fix: These lightweight transmissions weren't built for longevity. Complete rebuild with updated clutch packs and bands runs 12-16 hours labor. Many shops recommend the 200-4R swap over rebuilding a TH200C.
Estimated cost: $1,800-3,200
350 Diesel Engine Catastrophic Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: White smoke from exhaust on startup, Loss of coolant with no external leaks, Hard starting when warm, Sudden loss of power and heavy knocking
Fix: The Olds 350 diesel is notorious for head gasket failures, cracked heads, and failed injection pumps. Head studs pull out of the block. Rebuild requires machining and proper studs, 25-35 hours. Many owners swap to a gas 305 or 350 instead (20-25 hours).
Estimated cost: $4,500-7,000
Engine and Transmission Mounts Collapse
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Excessive engine movement during acceleration, Clunking when shifting into gear, Vibration through floorboard at idle, Difficulty shifting manual transmission if equipped
Fix: Rubber mounts deteriorate and separate. Transmission mount is a common failure point causing harsh shifts. Engine mounts run 2-3 hours, transmission mount 1.5-2 hours. Replace all three at once.
Estimated cost: $350-600
Carburetor Issues on V6 and V8 Gas Engines
Common · medium severitySymptoms: Rough idle and stalling when cold, Hesitation on acceleration, Black smoke from exhaust, Poor fuel economy (under 12 mpg city)
Fix: Rochester Quadrajet carbs develop vacuum leaks, worn throttle shafts, and stuck choke mechanisms. Rebuilds run 3-4 hours but often need repeated adjustment. Ethanol fuel accelerates deterioration of gaskets and diaphragms.
Estimated cost: $400-750
Rear Main Seal and Oil Pan Gasket Leaks
Occasional · medium severityTypical onset: 90,000-150,000 mi
Symptoms: Oil puddles under rear of engine, Oil spots on driveway after sitting overnight, Low oil level between changes, Oil coating on transmission bellhousing
Fix: Two-piece rear main seals are prone to leaking. Rear seal requires transmission removal, 8-10 hours. Oil pan gasket is simpler at 3-4 hours but access is tight. Often done together if transmission is already out.
Estimated cost: $600-1,400
Fuel System Varnish and Filter Clogging
Occasional · low severitySymptoms: Stalling after sitting for weeks, Difficulty starting after fillup, Loss of power under load, Surging at highway speeds
Fix: Ethanol fuel leaves varnish in carburetors and clogs inline fuel filters quickly. Filter replacement is 0.5 hours, but carburetor cleaning adds 2-3 hours. Tanks often have rust sediment requiring drop and clean (4-5 hours).
Estimated cost: $150-650
Cooling System Hose and Heater Core Failures
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Sweet coolant smell in cabin, Fogged windshield that's oily to touch, Overheating in traffic, Coolant loss with no visible external leaks
Fix: Original hoses crack and burst. Heater core failure is common and requires dash removal, 6-8 hours labor. Lower radiator hoses collapse internally causing overheating. Replace all hoses preventively.
Estimated cost: $450-900
Buy the 231 V6 version only, avoid the diesel at all costs, and budget $2,000 for deferred maintenance on any example—these are 40+ year old cars with weak transmissions.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.